The present invention relates generally to devices used to individually remove a flat item from a stack during a manufacturing process. More specifically, the present invention is directed to a robotic device that is capable of receiving a stack of flat items, removing each item individually from the stack, and feeding the individual item into a manufacturing process in a continuous cyclical manner.
Heretofore, a number of different types of devices have been developed for the purpose of removing a single flat sheet of material from a stack, and feeding each individual sheet into a manufacturing or printing process, or an assembly line. Most commonly, such destacking sheet feeders may be found in printers and copiers, where a stack of paper is loaded into a hopper, and the printer or copier feeds a single sheet at a time into the printing process, typically using mechanized rollers to remove the top sheet from the stack for printing.
Other types of destackers and sheet feeders have been developed, as well. U.S. Pat. No. 4,345,752 is directed to a sheet transport apparatus that picks up and transports a topmost sheet of a stack of sheets in a one-by-one manner by using a rotating suction drum to pick up the sheets. U.S. Pat. No. 5,494,398 discloses a device for unstacking tortillas and conveying them to a moving belt by using a rotating cylinder having holes in its surface through which suction acts on the tortillas. Other devices, similarly to printers and copiers, simply use rollers to frictionally engage one sheet or flat item at a time and slide it from the top of the stack.
One problem associated with various destacking devices is that it is difficult for the device to consistently move a single sheet, and sometimes multiple sheets are moved together, when the intent is to move one sheet at a time. Another problem is that rollers used to frictionally engage the stacked items sometimes wear down, creating a lower coefficient of friction, which causes the rollers to simply rotate against the item without forcing any movement thereof. Additionally, the use of suction drums and other suction devices requires the use of a vacuum system, which is a costly component and uses significant amounts of electricity to run. Thus, it would be desirable to provide a destacking device that overcomes these problems associated with the prior art, is inexpensive to manufacture, and consistently transports a single sheet or item at a time in a reliable manner.